The present invention relates to a venting arrangement for fuel tanks of motor vehicles with an expansion tank arranged above the maximum fuel level, connected with the interior of the fuel tank and extending in the vehicle transverse direction which is vented to the atmosphere by way of a vent or expansion line.
For fire protection reasons, the venting arrangement of fuel tanks is to be constructively so designed that certain safety conditions are fulfilled. One of the regulations in that connection provides that only a certain fuel quantity should flow out of the vent or expansion line of the vent arrangement during a limited time interval both during driving operation as also during a vehicle roll-over with several lateral rotations in any direction of rotation. Thereafter, no fuel must flow out anymore.
These safety conditions are fulfilled by a known vent arrangement which is installed in the interior of the tank but which has not been publicly described.
However, it has been found that in very special positions of fuel tanks equipped with such a vent arrangement, which are not encompassed by the safety regulations, it cannot be completely precluded that fuel can flow nonetheless into the atmosphere in a no longer tolerable quantity by way of the expansion or vent line.
It is therefore the object of the present invention to so improve a vent arrangement of the aforementioned type that also in very special positions deviating from the installed tank position, a fuel escape out of the expansion line beyond the permissive extent can no longer take place with certainty. Additionally, the construction of the vent arrangement is to permit the arrangement thereof inside or outside at the fuel tank or an arrangement separate therefrom.
The underlying problems are solved according to the present invention in that the expansion tank is vented into the atmosphere by way of an expansion or vent line which extends with a first line section starting from the expansion tank horizontally in the vehicle transverse direction up to near the plane of a tank side wall extending in the vehicle longitudinal direction and which extends with a second line section provided with a discharge orifice terminating the atmosphere in the direction toward a plane containing the oppositely disposed side wall and prevents in the inverted position of the fuel tank an outflow of fuel, in that the second line section includes at least one enlargement in proximity of the plane containing one of the tank side walls from which it extends away, in that fuel which flows out of the vent or expansion line sucks gas out of the enlargement when the tank is in a lateral position holding the enlargement above the fuel level, and in that the gas quantity present in the enlargement is sufficient up to the interruption of a siphoning action on the fuel produced inside of the enlargement.
With such a construction of the vent arrangement, in a tank side position in which the section of the expansion line having the enlargement assumes a position underneath the plane of the fuel level, fuel which has reached the expansion tank will flow into this section of the expansion or vent line and therewith also into the enlargement thereof forming a retaining chamber for a gas-air mixture.
The fuel rises thereby in the partial portion of this line section extending from the enlargement upwardly and finally terminating in the atmosphere, according to the principle of communicating pipes, to the level which the fuel has inside of the expansion tank, respectively, in the fuel tank whereas a gas volume remains enclosed in the enlargement. Owing to the fact that the partial line portion extending away from the enlargement into the atmosphere extends section-wise above the plane of the fuel level, the same remains free of fuel. Thus, in this lateral tank position no fuel will flow to the outside from the expansion line.
If the fuel tank is brought subsequently into the inverted (head) position and thereafter into the other side position, then the vent arrangement according to the present invention effects the following:
If the movement of the fuel tank into the inverted position of the tank takes place relatively slowly, then the expansion tank and the expansion or vent line are filled with fuel whereby in the enlargement thereof a certain gas volume remains again enclosed. An outflow of fuel out of the expansion line is prevented in this case, for example, in that the expansion line is so extended in relation to the fuel tank that the line end thereof terminating in the atmosphere is then again in a plane above the fuel level.
If the fuel tank subsequently reaches the other side position, then the section of the expansion or vent line having the enlargement will be located finally above the plane of the fuel level whereas the line end terminating in the atmosphere is disposed in a plane below the fuel level. In this case, only a part of the fuel present in the line section having the enlargement and more particularly only the permissive fuel quantity will then flow out of the same into the atmosphere. This is assured in that the fuel outflow comes to a standstill at a point in time while gas is continuously sucked off in this line section out of the enlargement and fuel is sucked into the enlargement by way of the line section of the expansion or vent line connected with the expansion tank (siphoning action), at which the vacuum produced by the outflowing fuel and thereby continuously becoming weaker is equal to or smaller than the vacuum which is necessary for the further suction of fuel into the enlargement. The volume of the enlargement is so selected for that purpose that the gas volume enclosed in the enlargement in the course of the first lateral tank rotation can continue to flow into the partial portion of the one line section terminating in the atmosphere at least until the pressure conditions in the two line sections of the expansion line terminating in the enlargement and leading away from the same are such that no fuel flows out any longer, respectively, the siphoning action is interrupted.
The vent arrangement equipped with an expansion or vent line having only one enlargement operates thereby reliably insofar as the line section having the enlargement terminates in the atmosphere within the area of the plane of the tank side wall which is disposed opposite the plane of the tank side wall, with respect to which the enlargement is adjacent.
According to a modified construction in accordance with the present invention, a line portion of the expansion or vent line which is connected ahead of the line section terminating in the atmosphere, passes over into the other line section within the area of the plane which is disposed opposite the plane containing the first tank side wall and contains the second tank side wall, and in that a further enlargement is provided in the line section near the plane containing the second tank side wall. This venting arrangement offers the advantage that the position of the end of the expansion or vent line which is open toward the atmosphere, can be provided at any desired distance with respect to the planes containing the tank side walls.
Reference in this application to the tank side walls extending in the vehicle longitudinal direction is not to be interpreted literally but is to be construed as applicable also to side walls insofar as they do not have an exact parallel position with respect to the vehicle longitudinal direction.
The expansion tank of the venting arrangement can be installed inside or outside of the fuel tank. In the former case, the expansion tank is to be arranged near the upper tank wall and the expansion or vent line is to be extended out of the fuel tank.
The expansion tank may thereby be constructed in different ways and may be provided, for example, according to a construction as described in the DE-PS No. 30 30 288.
In the second case, the expansion tank together with expansion or vent line may be arranged on the upper tank wall or at least section-wise at a distance above the same. With the latter constructional variation, the expansion tank may also be arranged on the tank top side, however, bridging a recess formed into the tank top side. Such a recess may form together with the expansion tank a window-like recess when the fuel tank is arranged, for example, behind the backrest of a rear seat bench and covers the same essentially on the back side, through which with a folded-down backrest, relatively long objects such as, for example, skis, can be extended for accommodation in the vehicle.
The expansion tank, however, may also be arranged as such at a distance above the upper tank wall. Such an arrangement is recommended insofar as passenger motor vehicles are to offer a through-loading possibility from the rear side, whose area is to correspond essentially to the overall width of the luggage space.
The present invention offers a considerable advantage insofar as it makes it possible to manufacture the expansion tank, the expansion or vent lines as well as the at least one enlargement as a molded part from plastic material in a cost-favorable manner. Insofar as the expansion tank is to be provided thereby at the upper tank wall on the outside thereof, the possibility exists to make these parts in one piece of plastic material whereby the construction may correspond, for example, to that of the DE-PS No. 24 40 397.